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  • INTERVIEW QUESTIONS C OPERATORS IN C DETAILS
    Question :
    What is a const pointer?
    Category Operators in C Interview Questions
    Rating (0.4) By 569 users
    Added on 10/22/2004
    Views 5531
    Rate it!
    Answers:

    The access modifier keyword const is a promise the programmer makes to the compiler that the value of a variable will not be changed after it is initialized. The compiler will enforce that promise as best it can by not enabling the programmer to write code which modifies a variable that has been declared const.

    A ?const pointer,? or more correctly, a ?pointer to const,? is a pointer which points to data that is const
    (constant, or unchanging). A pointer to const is declared by putting the word const at the beginning of the pointer declaration. This declares a pointer which points to data that can?t be modified. The pointer itself can be modified. The following example illustrates some legal and illegal uses of a const pointer:

    const char *str = ?hello?;
    char c = *str /* legal */
    str++; /* legal */
    *str = ?a?; /* illegal */
    str[1] = ?b?; /* illegal */




    const pointer: pointer is a constant which points the address of another variable

    we can't change the pointer(or
    otherwords can't change the
    address, pointer points to)

    char c[100]="Hello";
    char d[100]="Human";
    char *const ptr=c; //ptr points c
    ptr=d;/* Illegal*/
    ptr[3]='Y'; /* Legal*/

    pointer to const: The address pointed by pointer is constand that means we can't change the const location value using pointer

    char c[100]="Hello";
    char d[100]="Human";
    const char *p=c;
    p[2]='M'; /* Illegal */
    p=d; /* Legal */


    VENKATGOPU



    Posted by: VENKATGOPU    

    Contact VENKATGOPU Contact VENKATGOPU

    Pointer Constant is a pointer which points to the same location everytime. The address in the pointer variable can't be changed.
    Ex:
    int a=10,b=20;
    int const *p=&a;
    a=30;//Legal
    p=&b//Illegal: p a constant pointer always points to the same location

    But, Constant pointer always points to a value which cannot change i.e. the pointer can point to any variable but the value of the variable it points to cannot change.

    Ex:
    int a=10,b=20;
    const int *p=&a;
    a=30;//Illegal as p is a constant pointer the value it points to cannot change
    p=&b;//Legal



    Posted by: Samuka Mohanty    

    Contact Samuka Mohanty Contact Samuka Mohanty

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